Champions Yorkshire extended their lead to 227 with four first-innings wickets still in hand before the rain intervened, and Root looked in excellent form ahead of the first Test against Sri Lanka next week.
Play began on time and in just under an hour before the rain came the hosts added 71 to their overnight score to leave them on 557-6.
Root started the day on 190 and completed his double-century off 232 balls with 20 fours and a six.
Having moved comfortably to 213, Ravi Rampaul had Root aiming to leg only to get a leading edge that sailed straight to Gareth Batty at mid-off.
Adil Rashid played most of the stunning shots in the brief passage of play, with three consecutive boundaries of vintage quality at Tom Curran’s expense, two of the shots whistling through mid-off and the other being turned backward of square-leg.
Rashid was unbeaten on 60 from 85 balls at stumps, with Liam Plunkett four not out at the other end.
Head coach Jason Gillespie said after the call-off that he was confident Yorkshire could go on and win the match.
“We are already over 220 in front and will probably have to bowl pretty soon, but it will be up to the captain whether to declare straight away or bat for a bit longer – there is a fair chance to get a few runs as soon as we can,” he said.
Surrey wicketkeeper Ben Foakes said he thought his side had bowled quite well despite their opponents reaching 557-6.
“It became a bit easier once the effects of the new ball had worn off, but they still made batting look pretty easy,” he said.
“The rain has helped us so far and if we can get over the new ball we have a good chance of getting a draw.”
Test hopeful James Vince kept Lancashire at bay on an awkward morning for batsmen before rain came to Hampshire’s aid at Old Trafford.
Vince’s painstaking unbeaten 39 extended hope that his team could yet escape Manchester with a stalemate, all the more so after bad weather wiped out the last two sessions of their Division One fixture.
At stumps on day three, the visitors were still a mammoth 271 runs behind on 76-2 in their second innings.
But after Vince had blunted 147 deliveries, from an attack led by James Anderson (11-8-10-2), and Will Smith a further 91 in their unbroken stand of 53, Hampshire had a feasible escape route.
England coach Trevor Bayliss was in attendance three days ago, to see Vince run out without scoring by a brilliant piece of fielding from Steven Croft.
This time, in the two hours of play possible, the Hampshire captain put in a highly plausible audition for a maiden Test cap at No 5 – or even, his accustomed county position, No 3.
Vince, who had spent 45 balls up to stumps the previous evening, again had pedigree pace to contend with from England’s all-time leading Test wicket-taker as well as fiery New Zealand left-armer Neil Wagner.
Anderson struck with only his fifth ball of an increasingly grey day, opener Michael Carberry departing in a state of some bemusement, caught-behind on the back foot.
Vince was still taking no chances, and his new partner even fewer.
Smith spent 43 balls on nought, in fact, before clipping Wagner for a single to long-leg.
In an especially testing spell from round the wicket, Wagner almost brought the same fielder into play when instead Vince’s slightly mistimed hook flew just over Alviro Petersen’s head for six to bring up a hard-earned 50 stand.
It was no more than the Hampshire pair deserved and although there were more minor scrapes as Wagner dug in a succession of short deliveries, his victories were limited to the moral and partial.
When the forecast rain did set in, terminally, Vince had served his team and his own Test credentials equally well - pending Thursday morning’s squad announcement to face Sri Lanka.
There is every prospect nonetheless of much more hard work required on the final day here, before Hampshire can consider eking out an unlikely draw and/or Vince gets that call from the national selector.
Warwickshire versus Somerset and Middlesex against Nottinghamshire were completely washed out in Division One, as were three out of four matches in the second tier.
The only match that saw any action was at Canterbury where Gloucestershire sent down 46 overs against Kent.
They picked off five wickets for 174 in that time, two apiece for Josh Shaw and Craig Miles and one for Jack Taylor. Kent closed with a 141-run lead on 478-8.
Captain Sam Northeast turned his overnight 154 into 189 before being bowled by Shaw, all-rounder Darren Stevens posted a half-century and a late evening stand between Calum Haggett and Matt Hunn yielded 54 runs in just 6.5 overs.
Play was abandoned without a ball bowled in the games Leicestershire v Northamptonshire, Glamorgan v Worcestershire and Derbyshire v Sussex.